JP2007087804A - Surface treatment method and surface-treating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method and a surface-treating apparatus capable of reducing running costs and facility costs in the surface treatment method for repelling liquid in a base material to be treated by generating plasma under atmospheric pressure. <P>SOLUTION: The surface treatment method comprises a process for forming an electric field between a pair of opposing electrodes and generating plasma of treatment gas flowing in space in which the electric field is formed; and a surface treatment process for repelling liquid on the surface of the base material to be treated by plasma. The surface treatment process comprises surface treatment in first and second stages, and treatment gas used for the surface treatment in each stage comprises mutually different gas types or gas compositions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma surface treatment method for developing liquid repellency on a substrate surface using plasma, and more specifically, a surface treatment method using plasma in manufacturing processes of various devices such as semiconductor elements and liquid crystal display elements, and the like. Relates to the device.

  2. Description of the Related Art Conventionally, surface treatment methods that perform surface modification by generating glow discharge plasma under low pressure conditions have been disclosed / practically used. In the plasma treatment under these low pressure conditions, a high electric field is applied to a treatment gas corresponding to a target treatment to bring the treatment gas into a plasma state, and surface energy is generated using active species generated in the plasma. Is a surface treatment method for modifying the surface of a substrate by controlling. However, since the pressure for generating the plasma is low, the density of the active species is small, the processing speed is low, and the throughput of the apparatus itself is lowered. In addition, a vacuum chamber and a vacuum exhaust device for realizing a low-pressure environment are indispensable, and along with this, the means for transferring the substrate to be processed to the processing space is complicated. As a result, it has contributed to an increase in product cost. In recent years, as a method for solving this problem, plasma processing methods and apparatuses for generating plasma under a pressure near atmospheric pressure have been proposed, and processing with high uniformity can be performed in a relatively simple apparatus. Therefore, attempts are being made to expand into flat panel display fields such as LCD, PDP and EL.

  As an example of a plasma processing method for repelling the surface of a substrate to be processed by such a plasma surface treatment under a pressure near atmospheric pressure, a conventionally known plasma processing method and apparatus will be briefly described below ( For example, see Patent Document 1).

  FIG. 3 is an example of a conventional glow discharge plasma processing apparatus. In this plasma processing apparatus, a solid dielectric 116 is installed on a lower electrode 115 to which a DC power supply 111 is connected, and an upper electrode 114 to which the solid dielectric 116 and a high voltage pulse power supply (AC power supply) 110 are connected. Glow discharge plasma is generated in the space between. In addition to the electrodes, the surrounding vessel 112 includes a gas inlet 118, a dilution gas inlet 119, and gas outlets 120 and 121. The processing gas is supplied from the gas inlet 118, and the dilution gas is supplied from the gas inlet 119. Accordingly, they are respectively supplied to the discharge plasma generation space 113. Further, the surface treatment method in Patent Document 1 includes a pair of counter electrodes 114 and 115, and a solid dielectric 116 is installed on at least one of the counter surfaces of the electrodes. When a dielectric is installed, the substrate is placed in the space between the solid dielectric and the electrode, and when the solid dielectric is installed on both electrodes, the substrate is placed in the space between the solid dielectrics. The surface of the substrate to be treated is treated with the discharge plasma.

  Further, in the surface treatment, any surface treatment can be performed by selecting a gas (hereinafter referred to as a treatment gas) existing in the discharge plasma generation space 113, for example, a fluorine-containing compound gas as the treatment gas. By using, a fluorine-containing group is formed on the surface of the substrate to be treated, the surface energy is lowered, and a liquid repellent surface is obtained.

Further, in this conventional apparatus, from the viewpoint of safety, as the above-mentioned fluorine element-containing compound, carbon tetrafluoride (CF ₄ ) or hexafluoropropylene (CF ₃ CFCF ₂ ) that does not generate harmful gas hydrogen fluoride. ), Cyclobutane octafluoride (C ₄ F ₈ ) is preferably used, and from the viewpoint of economy, it is diluted with a rare gas such as helium or argon, or a diluent gas such as nitrogen gas, rather than the above atmosphere alone. It is considered preferable to perform the treatment in a controlled atmosphere.
JP-A-10-154598

  However, such a conventional plasma processing method has a problem that a sufficient liquid repellent effect cannot be obtained unless a large amount of fluorine-containing compound gas is used, and it is difficult to further reduce the running cost. Furthermore, when a fluorine-containing compound gas is used, it is necessary to decompose / detoxify the treated gas regardless of the amount used from the viewpoint of preventing global warming in recent years. Therefore, the more fluorine-containing compound gas is used, the more burden is placed on the decomposition / detoxification treatment equipment, resulting in an increase in equipment cost.

  In view of the above problems, the present invention provides a surface treatment method and apparatus capable of reducing running costs and equipment costs in a surface treatment method for generating plasma under atmospheric pressure to make a substrate to be treated liquid repellent.

  As a result of intensive studies / researches to solve the above-mentioned problems, the present inventor has achieved plasma surface treatment that has been conventionally performed in one stage in a plasma processing apparatus that can realize a stable discharge state under conditions near atmospheric pressure. A surface treatment method that can reduce running costs and equipment costs and alleviate adverse effects on the environment has been found by dividing the process into two stages, and the present invention has been completed. That is, by dividing the plasma surface treatment into two stages, the required amount of fluorine-containing compound gas in the processing gas is reduced, the running cost of the processing gas, and the processing / decomposition equipment for the processed gas are applied. Equipment costs can be reduced.

  That is, the present invention provides a step of forming an electric field between a pair of electrodes facing each other, converting the processing gas flowing in the space in which the electric field is formed into plasma, and a surface that makes the surface of the substrate to be processed liquid-repellent by the plasma The surface treatment step is composed of first and second stage surface treatments, and the treatment gas used for the surface treatment of each stage is composed of different gas species or gas compositions. A processing method is provided.

The surface treatment step may be performed under a pressure near atmospheric pressure.
The processing gas used for the first stage surface treatment may be composed of helium gas and nitrogen gas, and the processing gas used for the second stage surface treatment may be composed of helium gas and fluorine-containing compound gas.
The processing gas used for the first stage surface treatment may contain 5% by volume or more of nitrogen gas, and the processing gas used for the second stage surface treatment may contain 1% by volume or more of fluorine-containing compound gas.
The first stage surface treatment is performed by a direct method in which the surface of the substrate to be treated is directly exposed to plasma, and the second stage surface treatment is performed by a remote method in which the surface of the substrate to be treated is not directly exposed to plasma. Also good.

  Furthermore, this invention is provided with the 1st and 2nd surface treatment part from another viewpoint, each surface treatment part forms an electric field between a pair of electrodes which mutually oppose, and flows into the space in which the said electric field is formed It is characterized by comprising a surface treatment part for converting the treatment gas into plasma and lyophobizing the surface of the substrate to be treated by the plasma, and the treatment gas introduced into each of the surface treatment parts is composed of different gas species or gas compositions. A surface treatment apparatus is provided.

Each of the surface treatment units may make the surface of the substrate to be treated liquid repellent under a pressure near atmospheric pressure.
The processing gas used for the first surface processing unit may be composed of helium gas and nitrogen gas, and the processing gas used for the second surface processing unit may be composed of helium gas and fluorine-containing compound gas.
The first surface treatment unit employs a direct method in which the surface of the substrate to be treated is directly exposed to plasma, and the second surface treatment unit employs a remote method in which the surface of the substrate to be treated is not directly exposed to plasma. Also good.

  According to the surface treatment method and apparatus of the present invention, the required amount of compound gas contained in the treatment gas can be reduced, so that the running cost for the lyophobic treatment and the decomposition / detoxification equipment for the treated gas are achieved. It is possible to reduce the equipment cost required for the manufacturing process and contribute to the cost reduction of various device manufacturing processes such as semiconductor elements and liquid crystal display elements.

  Hereinafter, the surface treatment method according to the present invention will be described in detail. First, the structure of the surface treatment apparatus and the basic treatment procedure of the surface treatment method will be described, and then specific examples will be described. The present invention is also effective in a plasma processing apparatus having an electrode structure other than the electrode structure used in the description of the present embodiment, and is not limited to the surface treatment apparatus used in the present embodiment.

  First, the structure of a surface treatment apparatus for realizing the surface treatment method according to the present invention will be described. FIG. 1 is an example of an atmospheric pressure plasma apparatus that can be used in the surface treatment method of the present invention, and is a side cross-sectional view of the entire apparatus cut by a plane perpendicular to the river width direction through which the substrate flows. Here, the first electrode unit (A) and the second electrode unit (B) in FIG. 1 are units having the same configuration, and are arranged in parallel to perform two-stage continuous plasma processing. FIG. 2 is an enlarged view of a main part of the electrode unit.

  In the atmospheric pressure plasma apparatus shown in FIG. 1, the upper electrode unit 3 and the lower electrode unit 4 are arranged to face each other with a predetermined interval, and a high-frequency power source 51 is connected to the power transmission path 61, the upper electrode unit 3. 62, and a high-frequency power source 52 having the same frequency and a different phase as the high-frequency power source 51 is connected to the lower electrode unit 4 through power transmission paths 63 and 64. A substrate 31 to be treated is installed between the upper electrode unit 3 and the lower electrode unit 4, and the substrate 31 is conveyed at a predetermined speed in a predetermined direction by the substrate conveying roller 24. Yes. The two electrode units 3, 4 and the substrate 31 to be surface-treated are inside a space surrounded by the upper chamber 1, the lower chamber 2 and the upper electrode cover 32, and the upper chamber 1, the lower chamber 2, In between, the substrate carrying-in / out port 36 through which the substrate 31 to be processed can pass is provided in the front and back in the substrate traveling direction. A gas supply port 21 is provided in the upper electrode cover 3 and the lower chamber 2, and a processing gas necessary for processing is supplied from the gas supply port 21. In addition, the lower chamber 2 is provided with a gas exhaust port 22 so that the gas in the gas reservoir 23 can be discharged.

  In FIG. 2, the upper electrode unit 3 includes a voltage application side electrode 5, a ground side electrode 6, a voltage application side dielectric 7 and a ground side dielectric 8, and the ground side electrode 6 is connected to the high frequency power source 51 by a power transmission path 62. The voltage application side electrode 5 is connected to a high frequency power source 51 through a power transmission path 61. The voltage application side electrode 5 is surrounded by a voltage application side dielectric 7, and a ground side dielectric 8 is provided in a part of the ground side electrode 6, and a processing gas can pass between these dielectrics. An interval 10 is provided, and preliminary discharge can be performed at the interval 10. Further, a gas reservoir 9 is provided between the voltage application side electrode 5 and the upper electrode cover 3, and the processing gas supplied from the gas supply port 21 is once stored in the gas reservoir 9, and then the gas The gas passes through the flow path 11 from the gas outlet 12 and is supplied to the plasma processing space 25 through the interval 10. Similarly, the lower electrode unit 4 includes a voltage application side electrode 13, a ground side electrode 14, a voltage application side dielectric 15, and a ground side dielectric 16, and the voltage application side electrode 13 is connected to the high frequency power source 52 by a power transmission path 63. The ground-side electrode 14 is connected to the high-frequency power source 52 through a power transmission path 64. The voltage application side electrode 13 is surrounded by a voltage application side dielectric 15, and a ground side dielectric 16 is provided in a part of the ground side electrode 14, and a processing gas can pass between these dielectrics. A sufficient interval 17 is provided, and preliminary discharge can be performed in the interval 17. A gas reservoir 9 is provided between the voltage application side electrode 13 and the lower chamber 2, and the processing gas supplied from the gas supply port 21 is once stored in the gas reservoir 9, and then the gas flow path 18. Then, the gas is supplied from the gas outlet 19 through the interval 17 to the plasma processing space 25. The voltage application electrodes 5 and 13 and the ground electrodes 6 and 14 are each provided with a cooling water flow path 20 (mesh pattern in FIG. 2), and arrows indicate the flow direction of a gas such as a processing gas. ing.

Next, procedures / operations in performing the surface treatment will be described with reference to FIGS.
First, a processing gas in which a predetermined gas type is mixed at a predetermined ratio by a mass flow meter or the like is supplied from the gas supply port 21. The supplied processing gas once spreads in a direction perpendicular to the paper surface in the gas reservoir 9, passes through slit-like or shower-like gas flow paths 11 and 18 having a cross-sectional area sufficiently smaller than that of the gas reservoir 9, and gas It ejects toward the to-be-processed base material 31 via the intervals 10 and 17 from the ejection ports 12 and 19. FIG. On the other hand, the high-frequency power output from the high-frequency power source 51 passes through the power transmission path 61 to the electrode 5, and the high-frequency power output from the high-frequency power source 52 having the same frequency and the same phase as the high-frequency power source 51 differs from the power transmission path 63. To each of the electrodes 13 via. Thereby, an electric field is formed between the electrode 5 and the electrode 13. By this electric field, the processing gas ejected toward the base material 31 from the intervals 10 and 17 is converted into plasma in the plasma processing space 25 under atmospheric pressure. In addition, the atmospheric pressure in a present Example is a pressure range of 0.1 atmosphere or more and 2 atmospheres or less. By contacting / reacting the processing gas plasmified in the plasma processing space 25 and the substrate to be processed 31, a desired surface treatment is performed on the surface of the substrate to be processed 31, and the processing gas after the surface treatment reaction (used) After the gas is once accumulated in the gas reservoir 23, it is led to an abatement device through an exhaust port 22 by an exhaust pump or the like, decomposed / detoxified, and then discharged out of the processing system. When the surface treatment of the second stage is further performed on the substrate 31 to be treated, the surface of the second stage is similarly obtained by continuously conveying the inside of the adjacent second electrode unit (B). Perform the process.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the effect of this invention is not limited to a present Example.
(Examples 1-3, Comparative Examples 1-5)
In the present embodiment, a mixed gas of carbon tetrafluoride / helium / nitrogen is used as a processing gas, and the first stage and the second stage are performed under the conditions of gas types and gas compositions as shown in Examples 1 to 3 in Table 1. The surface treatment was continuously performed and the liquid repellency was evaluated. Moreover, as a conventional comparative example, the surface treatment of only one step was performed under the conditions of Comparative Examples 1 to 5 in Table 1, and liquid repellency was evaluated in the same manner as in the Examples.

  In addition, as a common condition in the examples and comparative examples, the interval of the plasma processing space 25 is 2.3 mm between the substrate 31 to be processed and the upper electrode unit 3, and 1 mm between the substrate 31 to be processed and the lower electrode unit 4. As the frequency, a frequency of 20 kHz, ± 9 kV was applied between the electrodes 5-6 and 13-14. In addition, a 0.7 mm thick glass substrate having an organic film containing carbon black (hereinafter referred to as CB) formed on the surface is used as the substrate 31 to be processed, and the substrate is conveyed at a speed of 1000 mm / min. Surface treatment was performed. The total amount of the processing gas is common to all Examples and Comparative Examples, and is 250 ml / min. It was.

  Further, the microscopic contact angle meter was used for evaluating the liquid repellency, and the contact angle was evaluated using an ether solvent as the dropping liquid. As measurement conditions, a capillary (capillary) having a tip diameter of 30 μm was used to drop / evaluate the solvent onto the surface of the treated substrate, and the average of the three measurement points was used as the contact angle of the sample.

  Table 1 shows the processing gas conditions and contact angle measurement results for each example and comparative example. Note that the contact angle of the surface of the substrate 31 to be treated before the treatment was 10 ° or less. For liquid repellency, for the sake of convenience, a contact angle of 50 ° or more is used as a measure of liquid repellency. did.

  As for the result of the conventional surface treatment of only one stage, the ratio of carbon tetrafluoride in the treatment gas is sufficient to obtain a sufficiently liquid-repellent surface as compared with the results of Comparative Examples 1 and 4 or Comparative Examples 2 and 5. It is understood that 5 vol% or more is necessary. Further, from the comparison of the results of Comparative Examples 2 and 3, the treatment gas consisting of only carbon tetrafluoride / helium does not provide sufficient liquid repellency, and nitrogen not only functions as a dilution gas but also exhibits liquid repellency. It has become clear that it plays an important role. Therefore, in the case of the conventional liquid repellency treatment by only one step, in order to obtain sufficient liquid repellency, all of carbon tetrafluoride / helium / nitrogen is included and the carbon tetrafluoride ratio is 5% by volume or more. It can be seen that a processing gas having a nitrogen ratio of 5% by volume or more is necessary.

  On the other hand, regarding the result of the two-stage surface treatment according to the present invention, as seen in Examples 1 and 2, the first-stage surface treatment using a treatment gas composed of only helium / nitrogen is performed. After that, when the second stage surface treatment is subsequently performed using the treatment gas consisting of only helium / 4-carbon fluoride, the volume of the carbon tetrafluoride in the treatment gas used for the second stage surface treatment is 1 volume. It was found that sufficient liquid repellency can be obtained even when the content is reduced to%. Further, from the results of Example 3, it was found that the liquid repellency was not lowered even when the nitrogen ratio in the first stage processing gas was reduced to 5% by volume.

(Examples 4 to 6)
Next, regarding the first and second surface treatments, the effect of whether the surface of the substrate to be treated was directly exposed to the plasma was examined. Where the surface treatment method is a “direct method” in which the surface of the substrate to be treated is directly exposed to plasma, but when the power supply to the lower electrode unit 4 is not performed in the surface treatment procedure, the interval 10, In the “remote method”, the active species converted into plasma by the preliminary discharge at 17 reaches the surface of the substrate to be treated and the surface treatment is performed. In Examples 4-6, the surface treatment of the 1st and 2nd step was continuously performed by the combination as shown in Table 2, and the liquid repellency and surface roughness were evaluated.
The other conditions were all the same as in Example 3.

Moreover, about surface roughness, Rms (surface mean square roughness) was measured using AFM (atomic force microscope), 3 points | pieces were measured, and the average value evaluated.
Table 2 shows the evaluation results of the contact angle and surface roughness of each example. Table 2 also shows the results of Example 3 as a comparative example.

  As a result, compared to the case where both the first and second stage surface treatments are performed by the “direct method”, the contact angle is not greatly reduced in any combination, and a sufficient liquid repellent surface is obtained. You can see that However, from the evaluation result of the surface roughness, the surface roughness of the final substrate surface to be treated is lower and higher when the second stage surface treatment is performed by the “remote method”. Liquid repellency is obtained. Therefore, considering the influence on the thin film to be formed after the surface treatment, it is more preferable to perform the first stage surface treatment by the “direct method” and the second stage surface treatment by the “remote method”. I understand.

  From the above results, even when the ratio of carbon tetrafluoride in the process gas is reduced to 1/5 of the conventional gas by performing the two-stage surface treatment according to the present invention, the conventional one-stage surface treatment is performed. It was found that a liquid-repellent surface similar to that can be obtained. From this, by performing the two-step surface treatment according to the present invention, it becomes possible to reduce the required amount of the fluorine-containing compound gas, which is the most expensive and the largest environmental load among the processing gases, to 1/5 of the conventional amount. As a result, the process running cost in the same lyophobic treatment and the equipment cost for introducing the abatement equipment can be greatly reduced.

In the present embodiment, a mixed gas of fluorine-containing compound / helium / nitrogen is used as a processing gas for generating plasma that makes the substrate surface lyophobic, of which carbon tetrafluoride (CF) is used as the fluorine-containing compound gas. ₄ ), but other fluorine-containing compound gases include carbon hexafluoride (C ₂ F ₆ ), propylene hexafluoride (CF ₃ CFCF ₂ ), and octafluorocyclobutane (C ₄ F ₈ ). Fluorine-carbon compounds, halogen-carbon compounds such as 1 chlorine trifluoride (CClF ₃ ), and fluorine-sulfur compounds such as sulfur hexafluoride (SF ₆ ). However, from the viewpoint of safety, it is preferable to use carbon tetrafluoride, propylene hexafluoride, or cyclobutane octafluoride that does not generate hydrogen fluoride, which is a harmful gas.

  In this example, a glass substrate having a thickness of 0.7 mm with a CB-containing organic film formed on the surface was used as a base material. However, this does not limit the scope of application of the present invention. In addition, the basic effects of organic films and plastics containing dyes and pigments remain unchanged. Other substrates include polyethylene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, acrylic resin plastic, glass, ceramic, metal, and the like.

In addition, examples of the shape of the substrate include plates and films, but the effect of the present invention is not particularly limited thereto, and may be arbitrary as long as it can be placed in the plasma processing space. Is possible.
Furthermore, in any of the examples, the liquid repellency was evaluated using an ether solvent, but this does not limit the scope of the present invention, and if it is essentially a liquid, it would be water. Even if it is alcohol, the degree of liquid repellency is the same, although there are differences. Further, the surface treatment apparatus is not limited to the electrode form as shown in the present embodiment, and the essential effect of the present invention is not changed in any surface treatment apparatus having any electrode shape. There is no.

  The embodiments and examples disclosed herein are illustrative and non-restrictive in every respect, and the scope of the present invention is defined by the terms of the claims, rather than the description above, and the claims It is intended that all changes within the meaning and scope equivalent to be included.

It is sectional drawing of the apparatus which can be used for the surface treatment method of this invention. It is a principal part enlarged view of the electrode unit part of the apparatus described in FIG. It is sectional drawing of the apparatus used for the conventional surface treatment method.

Explanation of symbols

(A) First electrode unit (B) Second electrode unit 1 Upper chamber 2 Lower chamber 3 Upper electrode unit 4 Lower electrode unit 5, 13 Voltage application side electrode 6, 14 Ground side electrode 7, 15 Voltage application side dielectric Body 8, 16 Ground side dielectric 9, 23 Gas reservoir 10, 17 Interval 11, 18 Gas flow path 12, 19 Gas outlet 20 Refrigerant 21 Gas supply port 22 Gas exhaust port 24 Base material transport roller 25 Plasma processing space 31 Substrate 32 Upper electrode cover 36 Substrate carry-in / out port 51, 52 High frequency power supply 61, 62, 63, 64 Power transmission path 110 High voltage pulse power supply 111 DC power supply 113 Discharge plasma generation space 114 Upper electrode 115 Lower electrode 116 Solid dielectric 117 Base material 118 Gas introduction port 119 Dilution gas introduction port 112 Pyrex (registered trademark) Manufacturing glass containers 120 and 121 gas discharge port

Claims (9)

  Including a step of forming an electric field between a pair of electrodes facing each other, converting the processing gas flowing in a space in which the electric field is formed into plasma, and a surface treatment step of making the surface of the substrate to be processed liquid-repellent by the plasma, The surface treatment method is characterized in that the surface treatment step comprises first and second stage surface treatments, and the treatment gases used for the respective stage surface treatments comprise different gas species or gas compositions.   The surface treatment method according to claim 1, wherein the surface treatment step is performed under a pressure near atmospheric pressure.   The process gas used for the first stage surface treatment is made of helium gas and nitrogen gas, and the process gas used for the second stage surface treatment is made of helium gas and a fluorine-containing compound gas. 3. The surface treatment method according to any one of 2.   The processing gas used for the first stage surface treatment contains 5% by volume or more of nitrogen gas, and the processing gas used for the second stage surface treatment contains 1% by volume or more of fluorine-containing compound gas. 4. The surface treatment method according to 3.   The first stage surface treatment is performed by a direct method in which the surface of the substrate to be treated is directly exposed to plasma, and the second stage surface treatment is performed by a remote method in which the surface of the substrate to be treated is not directly exposed to plasma. The surface treatment method according to claim 1, wherein:   First and second surface treatment sections are provided, each surface treatment section forms an electric field between a pair of electrodes facing each other, and plasma is formed from the processing gas flowing in the space where the electric field is formed. A surface treatment apparatus comprising a surface treatment section for making a treated substrate surface lyophobic, wherein treatment gases introduced into the respective surface treatment sections are composed of different gas types or gas compositions.   The surface treatment apparatus according to claim 6, wherein each of the surface treatment units repels the surface of the substrate to be treated under a pressure near atmospheric pressure.   The process gas used for the first surface treatment section is made of helium gas and nitrogen gas, and the process gas used for the second surface treatment section is made of helium gas and a fluorine-containing compound gas. The surface treatment apparatus according to any one of 7.   The first surface treatment unit adopts a direct method in which the surface of the substrate to be treated is directly exposed to plasma, and the second surface treatment unit adopts a remote method in which the surface of the substrate to be treated is not directly exposed to plasma. The surface treatment apparatus according to any one of claims 6 to 8.

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